The present invention relates to a four-jointed wiper arm assembly.
Wiper systems for motor vehicles having multiple windshield wipers are attached to the vehicle body using their wiper bearings directly or indirectly via a plate. A wiper motor with a built-in gearing drives, via a crank and joint rods, further cranks which are rigidly connected to a driveshaft for each windshield wiper.
Furthermore, it is possible that the output shaft of the wiper motor drives a four-jointed wiper arm assembly. This wiper arm assembly has a pivotable drive lever which sits on a drive axis and is flexibly connected to a link rod via a coupling element. The other end of the link rod sits on a fixed axis. Since the link rods are long, they require a relatively large amount of installation space. A fixing part of a wiper arm, to which a joint part of the wiper arm is fixed via a swing-down joint, is molded onto the coupling element. The drive lever can be driven directly by an output shaft of the wiper motor or via a crank and joint rods. The kinematics of the four-jointed wiper arm assembly causes a combined stroke-pivot movement of the windshield wiper. In this manner, the windshield wiper, the driveshaft of which is positioned more toward the center of the windshield, can follow the angular contour of a windshield better when the windshield wipers are synchronized, and this device is therefore frequently used in wiper systems to increase the field of view and comfort on the passenger side.
The wiping range of a windshield wiper is delimited by a parking position and a return position. The windshield wiper moves out from the parking position, which frequently is in the lower location in a hood gap between the engine hood and the windshield, upward to the return position and then back again.
The windshield wiper has a wiper arm, including the fixing part and a joint part coupled to it, onto which a wiper rod is coupled or molded. The free end of the wiper rod is flexibly connected to a wiper blade, a wiper strip of which with its wiper lip is moved over the windshield between the parking position and the return position during the pivot movement.
A wiper blade for cleaning curved windshields of motor vehicles is described in German Published Patent Application No. 36 21 233. In order to achieve good wiping results on a flat windshield, the wiper blade of a windshield wiper must be positioned so that its longitudinal central plane is perpendicular to the windshield when the wiper blade is unloaded, and a wiper lip molded on the wiper strip only touches the windshield surface. In spherically curved vehicle windshields, the slope of this longitudinal central plane to the windshield surface changes over the entire wiped area. Furthermore, the slope of the longitudinal central plane also changes in the longitudinal direction of the wiper blade. The optimum alignment described for a flat windshield can only be achieved during the wiper operation for spherically curved vehicle windshields at certain points and traveling in the longitudinal direction of the wiper blade. In this case, the deviations from the perpendiculars or the normals to the vehicle windshield, which are measured in angular degrees and are called perpendicular deviations or perpendicular errors, are greater in the more strongly curved side regions of the vehicle windshield than in the flat central regions. The flexibility of the wiper squeegee can only partially compensate for the perpendicular deviation.
In practice, the necessary setting angle of the wiper blade relative to the windshield and thus the perpendicular error is usually produced by slanting the output axes of the wiper linkage. The wiper blade therefore assumes a desired position which deviates from a perpendicular position relative to the vehicle windshield. Since wiper systems are characterized by a large length/width ratio, a great sensitivity of the angular position of the output axes and thus of the perpendicular error of the wiper blade results, particularly in the parking position. The manufacturing tolerances of the individual, numerous components of the windshield wiper and its drive are low, however, the sum of the tolerances, combined with those of the attachment to the vehicle body and of the body itself, is so large that an optimum setting angle is not ensured in mass production. To compensate for the manufacturing tolerances, the longitudinal central plane of the windshield wiper to the vehicle windshield is therefore set during assembly by setting the wiper arm so that the desired perpendicular error is achieved. The setting in the parking position, which is to allow the greatest possible bandwidth in regard to the setting angle, must not, however, lead to significant deviations in the return position of the windshield wiper.
A shaft-hub connection of a windshield wiper in which, in the connection region, the driveshaft has an offset and a cross-section which deviates from the circular, and is in particular polygonal, is described in German Published Patent Application No. 44 28 371. An edge of a recess of the fixing part presses against the offset or an intermediate disk, with the recess conically expanding toward the end of the driveshaft. A matching, conical clamping part, which is pressed by a nut against the fixing part, is inserted into the recess. The clamping part has a passage for the driveshaft, the cross-sectional profile of which corresponds to that of the driveshaft.
A similar shaft-hub connection of a windshield wiper is described in U.S. Pat. No. 3,085,821. The clamping part has a passage for the driveshaft which fits with a cylindrical or conical region of the driveshaft having a knurl and/or a toothed surface. Through the conical connection between the fixing part and the clamping part and, if necessary, through the conical connection between the clamping part and the driveshaft, the toothed surface of the fixing part and of the driveshaft is pressed into the surface of the clamping part, which was as smooth as possible up to this point, and permanently deforms it. For this purpose, the clamping part is made of an elastomer material or a relatively soft non-ferrous metal. In addition to the adhesion, a supporting positive connection is achieved by the many small lateral surfaces of the teeth.
According to an example embodiment of the present invention, in a parking position of the windshield wiper, the drive lever of a four-jointed wiper arm assembly encloses an angle xcex1 of approximately 90xc2x0 with the coupling element and is adjustable about an adjustment axis which extends approximately parallel to the coupling element and intersects the longitudinal axis of the driveshaft. The coupling element is connected to a link rod via a ball joint. Furthermore, a fixing part, on which a joint part with a wiper rod is coupled via a swing-down joint, of a wiper arm is attached or molded onto the coupling element. A wiper blade is flexibly connected to this wiper rod.
As the drive lever pivots about the adjustment axis, the coupling element is rotated around its longitudinal axis with the fixing part and the desired perpendicular error of the wiper blade is thus set. Setting may be easily performed in the parking position of the windshield wiper. The adjustment range may be +/xe2x88x923xc2x0. This is achieved in addition to the slanting of the two main axes of the drive lever.
The desired perpendicular error of the wiper blade may be freely selected during assembly of the windshield wiper, so that manufacturing tolerances do not negatively influence it. If the drive lever is rotated about the adjustment axis, the height of the coupling element changes. To prevent the four-jointed wiper arm assembly from being tensioned and the movement cycle from being blocked by this, it is possible for the coupling element to include two parts, with the first coupling part being coupled to the drive lever and being connected via a rotary joint, the rotational axis of which extends transverse to the longitudinal direction of the coupling element, to a second coupling part. This second coupling part is connected via a ball joint to the link rod. In this manner, the height displacement may be compensated.
In another example embodiment of the present invention, the contact surface between the clamping part and the drive lever forms a part of the surface of a sphere, while the bearing surface between the drive lever and the offset of the driveshaft forms a part of a lateral surface of a cylinder, the cylinder axis of which extends through the center of the sphere and parallel to the longitudinal direction of the wiper blade. In this manner, the drive lever and therefore the wiper arm are continuously adjustable about its longitudinal axis in a small overall installation space, if the bearing surface is smooth. A stepped adjustment is possible if the bearing surface has ribbing parallel to the cylinder axis. The ribbing may be used as a setting raster. Furthermore, the adhesive connection is supported by a positive connection, so that large forces may be transmitted.
The connection between the driveshaft and the drive lever may be secure and able to transmit large torques. However, it may not react so sensitively to the tightening torque of the screw connection that the setting selected is unintentionally changed when the screw is tightened. According to an example embodiment of the present invention, the cylinder axis of the bearing surface of the drive lever may extend through the sphere center of the contact surface between the clamping part and the drive lever, with the cylinder axis being, for example, within the attachment region of the drive lever.
According to another example embodiment of the present invention, the adjustment angle xc3xa41 or xc3xa42 of the drive lever about the cylinder axis of the bearing surface may be delimited by a stop. In this manner, setting angles which are completely unusable are kept from being unintentionally mounted on the vehicle. The stops enclose the optimum setting angle, from which deviating settings which are not optimum, but are usable, are possible. The stops are easily produced by an oblong hole in the drive lever which extends transverse to the cylinder axis and acts together with the driveshaft.
The cylindrical bearing surface may be molded directly onto the driveshaft, but it may be molded in a separate supporting plate which is supported on an offset of the driveshaft after assembly. The supporting plate is rotatably guided on the driveshaft, so that the longitudinal direction of the drive lever and therefore the longitudinal direction of the wiper arm may be rotated and aligned about the driveshaft axis, before the torque connection is produced by the clamping part and the screw. Simultaneously, the drive lever may be rotated about the adjustment axis between the two stops in order to set the setting angle of the wiper blade to the vehicle windshield.
The torque may be transmitted from the driveshaft via a noncircular profile, for example, one with a polygonal cross-section, to the clamping part, which transmits it predominantly through adhesion to the drive lever via the spherical contact surface. In this manner, the torque is transmitted on a small circumference by a secure positive connection, while the adhesion is provided on a larger diameter, and thus larger torques may be transmitted by smaller pressures. The adhesion may be supported by a positive connection in that the spherical surface of the drive lever is roughened or ribbed. In this case, the ribbing on the clamping part may extend at an angle to the ribbing on the drive lever, so that the directions intersect and a positive connection results which acts both in the direction of the torque to be transmitted and in the direction of the adjustment forces, with the ribbings being able to dig into one another. Manufacturing tolerances may also be compensated by the deformability of the ribbing.
According to another example embodiment of the present invention, the clamping part has grooves extending longitudinally on its circumference which end just before the larger end face. The grooves allow the clamping part to deform elastically and thus to adapt better to the depression of the drive lever. Since the grooves are not cut through up to the end face of the clamping part, but end just before it, a smooth end face is maintained. Furthermore, the grooves are protected toward the outside.
Before final assembly, some parts of the connection may be preassembled. For this purpose, on one hand, a locking ring made of plastic is used which rotatably attaches the supporting plate to the driveshaft and, on the other hand, in another example embodiment of the present invention, a plastic clip is used which clamps the supporting plate to the drive lever so it may pivot about the cylinder axis. In this case, the drive lever has a shoulder on which the plastic clip is held. Furthermore, the plastic clip is able to engage with projections in recesses of the drive lever.